Process for the preparation of lincomycin compounds

ABSTRACT

A simplified process for obtaining active lincomycin compounds of the formula   WHEREIN R1 is an alkyl of four to seven carbon atoms, inclusive, and wherein X is selected from the group consisting of 7(R)hydroxy and 7(S)-chloro, consists of two steps: (1) condensing a 1-carbobenzoxy-4-alkylproline (all four isomers) wherein the alkyl group has four to seven carbon atoms, inclusive, and a methyl thiolincosaminide (III) of the formula:   WHEREIN X is defined as herein described above, in water or acetone-water solution; separating the soluble from the insoluble fraction; and (2) removing the protective carbobenzoxy group by hydrogenolysis, separately from each fraction; to obtain an active trans-L and cis-L-lincomycin compound of the formula I above, and separately an analogous trans-D and cis-D-lincomycin product.

United States Patent 1 Magerlein PROCESS FOR THE PREPARATION OF LINCOMYCIN COMPOUNDS [75] Inventor: Barney J. Magerlein, Portage, Mich.

[73] Assignee: The Upjohn Company, Kalamazoo Mich.

22 Filed: Nov. 18,1970

211 Appl.No.: 90,846

Related US. Application Data [63] Continuation-impart of Ser. No. 796,558, Feb. 4,

1969, Pat. No. 3,634,043,

[52] US. Cl. ..260/210 R [51] Int. Cl. ..C07c 47/18 [58] Field of Search ..260/210 R [56] References Cited UNITED STATES PATENTS 3,496,163 2/1970 Birkenmeyer et al ..260/210 R Primary Examiner-Lewis Gotts Assistant Examiner-Johnnie R. Brown Attorney-l-lans L. Berneis and John Kekich 5 7 ABSTRACT A simplified process for obtaining active lincomycin compounds of the formula Feb. 6, 1973 has four to seven carbon atoms, inclusive, and a methyl thiolincosaminide (III) of the formula:

wherein X is defined as herein described above, in water or acetone-water solution; separating the soluble from the insoluble fraction; and (2) removing the protective carbobenzoxy group by hydrogenolysis, separately from each fraction; to obtain an active trans-L and cis-L-lincomycin compound of the formula I above, and separately an analogous trans-D and cis-D-lincomycin product.

6 Claims, N0 Drawings PROCESS FOR THE PREPARATION OF LINCOMYCIN COMPOUNDS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 796,558, filed Feb. 4, 1969, now US. Pat. No. 3,634,043.

EACKGROUNEGF'TPIEINVENTICSN perior and/or different antibiotic spectra with respect to bacteria, as well as different activities versus certain Plasmodia which produce human and/or animal malaria. Particularly advantageous modifications are: replacement of the propyl group on the proline moiety by a longer chain alkyl radical, e.g., butyl, pentyl, hexyl, or heptyl; replacement of the l'-methyl group with hydrogen; and replacement of the 7(R)-hydroxy group by 7(S)-chloro. 7(S)-chloro-7-deoxylincomycin is a lincomycin compound known by the generic name clindamycin.These modified lincomycins can preferably be synthesized by fist preparing a corresponding proline, e.g., one with a pentyl group in the 4-position, and condensing it with a methyl thiolincosaminide. Since the synthetically-prepared proline has two asymmetric centers and thus exists in four isomeric forms, cis-L, cis-D, trans-L, and trans-D, four final lincomycin compounds are obtained. Of these linthe cis-L-form is second in activity, and the two D- forms are of low or no activity. By an L-lincomycin compound is meant one in which the prolyl moiety is in the L-form, as in lincomycin itself. By a D-lincomycin compound is meant one in which the prolyl moiety is in the D-form. The terms trans and cis refer to the relative positions of the 4-alkyl and 2-carboxyl groups of the prolyl moiety.

conventionally, substituted the four isomeric 0 prolines would be separated, for example as the diastereoisomers, before condensation with the methyl thiolincosaminide. However, this separation has been found to be difficult, incomplete and costly.

In the present invention process the substituted proline, protected by a carbobenzoxy group on the lnitrogen, is condensed with the selected methyl thiolincosaminide in a solvent system which essentially quantitatively separates the resulting L-cis and Ltrans from the D-cis and D-trans lincomycins by selectively keeping one of the two fractions in solution and precipitating the other. The solvents useful for this reaction are acetone and acetonitrile, each with water present. In the case of 7(R)-0H-type lincomycin compounds the L-prolyl forms remain in solution while the D-prolyl forms precipitate; whereas in the 7(S)-Cl-type lincomycin compounds the D-prolyl forms remain in solution while the L-prolyl forms precipitate.

After hydrogenolyzing the carbobenzoxy group from the desired L-cis and L-trans fraction, a highly active antibiotic is produced in good yield.

The process and resulting products of this invention can be represented illustratively by the following forcomycin products, the trans-L-form is the most active, mulas:

' (ilbz- (llbz C O OH C O OH N N /N N V i I I COOH I COOH R1 R1 D-cis D-trans L-trans L-ciS HzN- in acetonitrile or acetone triethylamine HO isobutylchloroformate OH l/ S CH:

Filtration Filtrato Prccipitato hydrogcnolysis hydrogcnolysls sopurutuly obtained H CH3 N H If H N (J0N- I O-N no K ()ll 1 \l 1/ sun; \I J/ HUlIs OH )H L-cis and L-trzu 1S wherein Cbz symboly zes the carbobenzoxy moiety R is alkyl of four to seven carbon atoms, inclusive, and X is 7(R)-Ol-l or 7(S)-Cl.

DESCRIPTION OF THE PREFERRED EMBODIMENT Staphylococ- Salmonella cus Escherichia schottaureus S. aureus coli muelleri OSU 284 UC 552 ATCC 28 ATCC 9149 Lincomycin 0.4 0.8 400 4000 1'-Demethyl- 0.025 0.025 12.5 12.5 4'-depropy1 4-pentylclindamycin The starting materials of this invention are known in the art, e.g., disclosed in U. S. Pat. No. 3,496,163, patented Feb. 17, 1970, U. S. Pat. No. 3,514,440, patented May 26, 1970, U. S. Pat. No. 3,366,624, patented Jan. 30, 1968, and other patents.

ln carrying out the process of the present invention, a selected 1-carbobenzoxy-4 alky1proline (all four isomeric forms) is dissolved in acetonitrile or acetone with triethylamine present and then reacted with isobutyl chloroformate. To this solution after 10-30 minutes there is added a solution of the selected methyl thiolincosaminide in water or aqueous acetone. This mixture is stirred for A to 6 hours at a temperature between 10 and 40 C., conveniently at room temperature, 2230 C. Filtration gives a solution and a solid. Separation of there two phases and separate hydrogenolysis of each phase with platinum or palladium-on-carbon catalyst and hydrogen, provides an active antibiotic mixture of cis-L- and trans-L-antibiotics and a less active mixture of cis-D and trans-D-antibiotics. 1n the preferred embodiment a 5-10 percent palladium on charcoal catalyst is used in the hydrogenolysis, in a ratio of 1 part of catalyst to 2 to 4 parts of the carbobenzoxy-protected lincomycin compound. The reaction generally is carried out at room temperatures for a period of 1 to 48 hours. At the termination of the reaction, the mixture is filtered to remove the catalyst, the filtrate is evaporated and the residue is purified by conventional methods, e.g., chromatography, extraction, and recrystallization.

The following Preparations and Examples illustrate the novel process of this invention:

Preparation] N-Carbobenzoxy-4-pentylproline To a solution of 27.5 g. of 4-pentylproline hydrochloride in 450 ml. of water and 72.5 ml. of 4N aqueous sodium hydroxide are simultaneously added over 30 minutes 26 ml. of carbobenzoxy chloride and 415 ml. o14N aqueous sodium hydroxide. After stirring for 1.5 hours, the basic solution is extracted twice with ether. The aqueous solution is acidified, extracted several times with ethyl acetate, and the extracts evaporated to yield N-carbobenzoxy 4-pentylproline (37.2 g., 94 percent) as an oil.

Example 1 Methyl (4'-cisand trans-pentyl-l-carbobenzoxy-L- and D-prolyl)-7-deoxy-7(S) chlorothiolincosaminide.

a tag... I

D (trans and els) Cbz |-(l) SCH; H

L (trans and ois) Cbz=carbobenzoxy.

To a solution of 13.3 g. of a mixture of l-carbobenzoxy-L- and D-4-cis-pentylproline and l-carbobenzoxy L- and D-4-trans-pentylproline in 300 ml. of acetonitrile containing 5.3 ml. of triethylamine is added 5.1 ml. ofisobutyl chloroformate with cooling. After 15 minutes a solution of 10.2 g. of methyl 7-deoxy-7(S)- chlorothiolincosaminide in 250 ml. of 50 percent aqueous acetone is added. The mixture is stirred at ambient temperature for 3 hours. The solution is filtered to give 3.1 g. of methyl (4'-cisand trans-pentyl-1-carbobenzoxyL-pro1yl-7-deoxy-7(S)- chlorothiolincosaminide 111 above of melting point l99-201 C. dec. The filtrate is concentrated to about 50 percent of its volume. Filtration yields about 10 g ofa sticky solid. Recrystallization from acetone gives 3.8 g. of 111 with melting point 189-190 dec. A third crop of crystals of melting point 204-206 C. and weighting 400 mg., precipitates on standing.

The yield of the three fractions is 46.8 percent. in a similar experiment recrystallization from acetone affords methyl (4-cisand trans-pentyl-l -carbobenzoxy-L-prolyl)-7-deoxy-7(S)-chlorothiolincosaminide of melting point 208-2l0 C. and rotation [11],, =132 (MeOH).

Anal. Calcd. for C ,H ,CIN O .,S:

C, 56.58; H, 7.21; N, 4.89.

Found: C, 56.33; H, 7.26; N, 4.66.

Experiments show that the mother liquors contain essentially the D-isomer.

EXAMPLE 2 1'-Demethyl-4'-depropyl-4'-cisand trans-pentylclindamycin and its hydrochloride.

A mixture of 10.2 g. of l'-demethyl-1-carbobenzoxy-4-depropyl-4-cisand trans-pentylclindamycin 190 ml. of methanol and 3.8 g. of percent palladium on carbon is shaken under 40 lbs. hydrogen pressure for 18 hours. The mixture is then filtered, the filtrate distilled in vacuo mm. Hg) to give a residue of 7.0 g. of 1'-demethyl-4-depropyl-4-cisand trans-pentylclindamycin. This material is chromatographed over 700 g. of silica gel using chloroform-methanol (4:1) for elution. Fractions containing the desired compound as monitored by thin layer chromatography are collected; total weight 2.6 g. Conversion to the hydrochloride gives 1.9 g. of 1'-demethyl-4'-depropyl-4-cisand trans-pentylclindamycin hydrochloride of melting point l65l68 C. Recrystallization from aqueous acetone raises the melting point to 17 ll73 C. Anal. Calcd for C|9H3QCI2N2O5SI C, 47,99; H, 7.63; N, 5.89; S, 6.74; Cl, 14.91. Found: C, 47.83; H, 7.58; N, 5.67; S, 6.78; CI, 15.00. (corrected for 3.50% H O) EXAMPLE 3 1-Carbobenzoxy-l '-demethyl-4'-depropyl-4'-cisand trans-n-pentyllincomycin and l-Carbobenzoxy-1'- demethyl-4'-depropyl-4'-cisand trans-n-pentyl-D-lincomycin.

lsobutyl chloroformate (7.1 ml.) is added at 0 C. to a solution of 16.5 g. of N-carbobenzoxy-4-pentylproline (all four isomers) and 7.25 ml. of triethylamine in 300 ml. of acetonitrile. After 15 min. a solution of 13.1 g. of methyl thiolincosaminide in 150 ml. of water is added with vigorous stirring. The reaction mixture is stirred at ambient temperature (21.24" C.) for 3 hours. The crystals which precipitate are collected by filtration, washed with aqueous acetonitrile and dried. This is the undesired D isomer, 1-demethyl-1'-carbobenzoxy-4'-depropyl-4'-transand cis-n-pentyl-D- lincomycin of melting point l88197 C, and weight 10.75 g., (37.6 percent yield). Recrystallization form methanol affords 7.65 g. of pure material of melting point 198-207 C. and rotation [01],, +l77 (MeOH). Anal. Calcd. for C l-1 N O S:

C, 58.46;H, 7.63;N, 5.05;S, 5.7.

Found: C, 58.29; H, 7.52; N, 5.07; S, 5.84.

The mother liquor from the above separation is concentrated under vacuum and cooled. Filtration yields 12.05 g. (42.0 percent) of gummy solids of melting point 150-162. This material is recrystallized from acetone-methanol to yield 5.75 g. of the desired 1'-carbobenzoxy-l-demethyl-4'-depropyl-4'-cisand transn-pentyllincomycin of melting point 169-173 C. and rotation [01],, +1 16 (MeOH). Additional crops of this product are obtained at melting point 157l80 C., rotation [a]+9 1, 2.0 g.; of melting point 158-163 C., rotation [al +107, 1.03 g. All three crops of 1'- demethyl-l '-carbobenzoxy-4'-depropyl-4'-cisand trans-n-pentyllincomycin are used in the succeeding step.

Anal. Calcd. for C H N O S:

C, 58.46; H, 7.63; N, 5.05; S, 5.7. Found: C, 58.37; H, 7.56; N, 4.85; S, 5.57.

EXAMPLE 4 1-Demethyl-4'-depropyl-4'-cisand trans-n-pentyllincomycin and its hydrochloride.

A mixture of 8 g. of l'-carbobenzoxy-l '-demethyl-4' -depropyl-4-cisand trans-n-pentyllincomycin from above and 3 g. of 10 percent palladium on carbon in ml. of methanol is shaken under hydrogen pressure for 18 hours. The catalyst is removed by filtration. The methanol is distilled under vacuum to give 1- demethyl-4'-depropyl14-cisand trans-pentyllincomycin. The material is dissolved in 60 ml. of acetone and 3.8 ml. of 6 N HCl are added. The crystalline salt, 1-demethyl-4'-depropyl-4-cisand trans-n-pentyllincomycin hydrochloride, collected and dried. The yield of this hydrochloride of melting point 206208 C., rotation [01],, +1 35 (H O), is 5.0 g.

EXAMPLE 5 Methyl (4'-cisand trans-butyl-l'-carbobenzoxy-L- and D-propyl)-7-deoxy-7(S)-chlorothiolincosaminide.

In the manner given in Example 1, l-carbobenzoxy- 4-isobutyl chloroformate in the presence of triethylamine and thereafter with methyl 7-deoxy-7- (S)-chlorothiolincosaminide in aqueous acetone gives a precipitate of methyl (4-cisand t'rans-butyl-1'-carbobenzoxy-L-prolyl)-7-deoxy-7(S)-chlorothiolincosaminide and a solution containing the D-prolyl analogues.

EXAMPLE 6 Methyl (4-cisand trans-butyl-L-prolyl)-7-deoxy)- 7(S)-chlorothiolincosaminide.

In the manner given in Example 2, methyl (4-cisand trans-butyl-l-carbobenzoxy-L-prolyl)-7-deoxy- 7(S)-chlorothiolincosaminide in methanol is hydrogenolyzed with a 10 percent palladium on carbon catalyst to give methyl (4'-cisand trans-butyl-L- prolyl)-7-deoxy-7(S)-chloro-thiolincosaminide.

EXAMPLE 7 EXAMPLE 8 Methyl (4'-cisand trans-hexyl-L-prolyl)-7-deoxy- 7(S)-chlorothiolincosaminide.

1n the manner given in Example 2, methyl (4'-cisand trans-hexyl-l'-carbobenzoxy-L-prolyl)-7-deoxy- 7(S)-chlorothiolincosaminide in methanol is hydrogenolyzed with a 10 percent palladium on carbon catalyst to give methyl (4-cisand trans-hexyl-L- prolyl)-7-deoxy-7(S)-chlorothiolincosaminide.

EXAMPLE 9 Methyl (4'-cisand trans-heptyl-l'-carbobenzoxy-L- and D-prolyl)-7-deoxy-7(S)-chlorothiolincosaminide.

1n the manner given in Example 1, l-carbobenzoxy- 4-heptyl-L- and D-proline (all four isomers) in acetone is reacted with isobutyl chloroformate in the presence of triethylamine and thereafter with methyl 7-deoxy- 7(S)-chlorothiolincosaminide in 50 percent aqueous acetone to give a precipitate of methyl (4'-cisand trans-heptyl-l '-carbobenzoxy-L-prolyl)-7-deoxy-7(S)- chlorothiolincosaminide and a solution containing the D-prolyl analogues.

EXAMPLE l Methyl (4-cisand trans-heptyl-L-prolyl)-7-deoxy- 7(S)-chlorothiolincosaminide.

In the manner given in Example 2, methyl (4'-cis and trans-heptyl-l carbobenZoxy Dp rolyD-7 deoxy-7 chlorothiolincosaminide in methanol is hydrogenolyzed with a percent palladium on carbon catalyst to give methyl (4'-cisand trans-heptyl-L- prolyl)-7-deoxy-7(S)-chlorothiolincosaminide.

EXAMPLE 1 1 EXAMPLE l2 Methyl (4'-cisand trans-heptyl-L-prolyl) thiolincosaminide.

In the manner given in Example 4, methyl (4'- cis and trans-heptyl-l 'carbobenzoxy-L-prolyl)-thiolincosami nide in methanol is hydrogenolyzed with a 10 percent palladium on carbon catalyst to give methyl (4'-cisand trans-heptyl-L-prolyl)thiolincosaminide.

EXAMPLE [3 Methyl [4'-cisand trans-(2-methylpentyl)-l-carbobenzoxy-L- and D-prolyl]thiolincosaminide.

In the manner given in Example 3, l-carbobenzoxy- 4-(2-methylpentyl)proline (all four isomers) in acetonitrile is reacted with isobutyl chloroformate in the presence of triethylamine and thereafter with methyl thiolincosaminide in water to give a precipitate of methyl [4-cis and trans-(2-methylpentyl)-l'-carbobenzoxy-D-prolyl] triolincosaminide and a solution containing the L-prolyl analogue, which is isolated by evaporating the solvent, and recrystallized to give pure methyl [4'-cisand trans-(2-methylpentyl)-l '-carbobenzoxy-L-prolyllthiolincosaminide.

EXAMPLE l4 Methyl [4'-cisand trans-(2-methylpentyl)-L- prolyl]thiolincosaminide.

In the manner given in Example 4, methyl [4'-cisand trans-(2-methylpentyll-l -carbobenzoxy]-L- prolyl)thiolincosaminide in methanol is hydrogenolyzed with a l0 percent palladium on carbon catalyst to give methyl [4-cisand trans-methylpentyl)-L-prolyl]thiolincosaminide.

in the manner given in Examples 1 and 2 or 3 and 4 other (4'-cis and trans-alkyl-L- and D-prolyl)-7-deoxy- 7(S)-chlorothiolincosaminides are prepared.

Representative compounds thus obtained include: methyl (40-cisand trans-isobutyl-L- and D-prolyl)-7- deoxy-7(S)-chlorothiolincosaminide; methyl (4'-cisand trans-isopentyI-L- and D-prolyl)-7- deoxy-7(S)-chlorothiolincosaminide; methyl ]4'-cisand trans-(3-ethylpentyl)-L- and D- prolyl]-7-deoxy-7(S)-chlorothiolincosaminide; methyl (4'-cisand trans-butyl-L- and D-prolyl)thilincosaminide; methyl (4'-cisand trans-hexyl-L- and D-prolyl)thiolincosaminide; and the like.

lclaim:

1. A process for the production of an active 1- demethyllincomycin compound of the formula:

where R, is an alkyl of four to seven carbon atoms, inclusive; and wherein X is selected from the group consisting of 7(R)-hydroxy and 7(S)-chlor0, which comprises:

l. reacting, in acetonitrile or acetone solution, isobutyl chloroformate with a mixture consisting of lcarbobenzoxy-4-cisand trans-alkyl-L- and D- proline where the 4-alkyl group is R,, defined as above, and a trialkylamine, followed by an addition ofa methyl thiolincosaminide of the formula:

wherein X is defined as above, in an acetone or aqueous acetone solution, separating the insoluble from the soluble fraction; and

2. removing the protective carbobenzoxy group by hydrogenolysis from each fraction separately to obtain an active cisand trans L- l-demethyllincomycin of the formula 1 above and separately a cisand trans D-l -demethyllincomycin.

2. The process ofclaim 1 wherein the hydrogenolysis is performed with a palladium on carbon catalyst in methanol.

3. The process of claim 1, wherein the trialkylamine is triethylamine.

4. The process of claim 1, wherein R is pentyl and X is (S)-chlorine, so that the product is a l-demethyl-4- depropyl-4-pentylclindamycin.

5. In a process for the production of an active l-demethyllincomycin compound of the formula:

wherein R is analkyl of f our to seven carbon atoms, inclusive; the step which comprises:

1. reacting in acetonitrile or acetone solution isobutyl chloroformate with a mixture consisting of lcarbobenzoxy-4-cisand trans-alkyl-L- and D- proline wherein the alkyl group is R defined as above and a trialkylamine, followed by an additional of methyl thiolincosaminide of the formula:

bobenzoxy-4-depropyl-4'-cisand trans-alkyl-D-lincomycin from the soluble l'-demethyl-l'-carbobenzoxy- 4'-depropyl-4'-cisand trans-alkyl-L-lincomycin.

6. In a process for the products of an active 1'- demethyl lincomycin compound of the formula:

SGHa OH whereiiili ;isaiiai kfl straw to seven carbon atoms, inclusive; the step which comprises:

1. reacting in acetonitrile solution isobutyl chloroformate with a mixture consisting of l-carbobenzoxycisand trans-alkyl-L- and D-proline wherein the alkyl group is R defined as above and a trialkylamine, followed by an addition of methyl 7- deoxy-7(S)-chloro thiolincosaminide of the for-' mula:

in acetone-water; separating the insoluble l-demethyll-carbobenzoxy-4'-depropyl-4'-alkylclindamycin in which R, is defined as above, from the soluble fractions containing the D-clindamycin analogues. 

1. A process for the production of an active 1''-demethyllincomycin compound of the formula:
 1. reacting, in acetonitrile or acetone solution, isobutyl chloroformate with a mixture consisting of 1-carbobenzoxy-4-cis- and trans-alkyl-L- and D-proline where the 4-alkyl group is R1, defined as above, and a trialkylamine, followed by an addition of a methyl thiolincosaminide of the formula:
 1. reacting in acetonitrile or acetone solution isobutyl chloroformate with a mixture consisting of 1-CARBOBENZOXY-4-cis- and trans-alkyl-L- and D-proline wherein the alkyl group is R1, defined as above and a trialkylamine, followed by an additional of methyl thiolincosaminide of the formula:
 1. reacting in acetonitrile solution isobutyl chloroformate with a mixture consisting of 1-carbobenzoxy-cis- and trans-alkyl-L-and D-proline wherein the alkyl group is R1, defined as above and a trialkylamine, followed by an addition of methyl 7-deoxy-7(S)-chloro thiolincosaminide of the formula:
 2. removing the protective carbobenzoxy group by hydrogenolysis from each fraction separately to obtain an active cis- and trans L- 1''-demethyllincomycin of the formula I above and separately a cis- and trans D-1''-demethyllincomycin.
 2. The process of claim 1 wherein the hydrogenolysis is performed with a palladium on carbon catalyst in methanol.
 3. The process of claim 1, wherein the trialkylamine is triethylamine.
 4. The process of claim 1, wherein R1 is pentyl and X is (S)-chlorine, so that the product is a 1''-demethyl-4''-depropyl-4''-pentylclindamycin.
 5. In a process for the production of an active 1-de-methyllincomycin compound of the formula: 